Three-dimensional models of molecular structure are in effect a number of interconnected modules made of, e.g., plastics. Such modules can be shaped as hemispheres, ellipsoids, hemispheres with cut-off surfaces, or polyhedra. Each module simulates an atom, its radius corresponding to the van der Waals' atomic radius, while the distance from the center of the module to its cut-off surface corresponds to the covalent atomic radius. The elements linking the modules together simulate interatomic bonds, while the angles included between the geometric axes of the linking elements represent the valence angles. Swivel of some individual modules or complexes thereof simulate conforming spatial displacement of atoms.
Some prior-art three-dimensional models of molecular structures are known to comprise modules made as solid spherical elements. The modules are interlinked through connecting elements which are in fact split metallic sleeves having a narrow central portion and adapted to fit into the plain-walled module sockets (cf., e.g., a set `Eugon` developed at the organic and plastics industry research institute in the city of Budapest, Hungarian People's Republic).
However, it is due to the plain surface of the connecting elements that the sleeves are liable to gradually come out of engagement with the module sockets as the module rotates, thus disturbing the integrity of the three-dimensional model and accuracy of molecular structure simulation. It is also inconvenient that a special device, viz., pliers, should be used to join the modules. In addition the narrower portion of the sleeves is liable to break rather frequently. All this limits applications of modules of the afore-mentioned type to simulation of but relatively small molecular structures.
Another prior-art three-dimensional model of molecular structures comprises plastic modules, each of which representing one atom of the molecular structure being simulated. The modules are shaped as a sphere, hemisphere, ellipsoid, or polyhedron, wherein some portions of their surface can be cut off. The modules are hollow, and their walls are perforated, the perforations being situated at the center of intersecting planes. Each perforation is tapered and has an angle of taper of 4.degree., its narrower portion facing the center of the element and being surrounded by a stepped projection that restricts the entrance into the module interior.
The modules are interlinked through connecting elements shaped as two cone frustums joined together with their greater bases. The outer surface of these cone frustums are provided with recesses or grooves which engage stepped ridges or projections in the perforations of the modules when the latter are joined together (cf., e.g., U.S. Pat. No. 3,170,246 (1965).
A disadvantage of such three-dimensional models is in their sophisticated construction accounted for by intricate configuration of the connecting elements and perforations in the modules. The aforementioned type of interlinking the modules in practicable with small-sized modules only, which would be more convenient to produce by once-through casting from technological viewpoint. Moreover, the interlinking of modules in such a three-dimensional model is too flexible so that, when simulating large molecules, it is impossible to distinguish between changes developed by the models due to true conforming displacement and those caused by imperfection of construction.
The heretofore known three-dimensional models of molecular structures are assembled by fitting the connecting elements in the sockets or perforations of the modules, making good use of special devices. For instance, use is made of a tool to expand the perforations in the module, which is in effect a cant scraper having a handle and a tip that, when rotated in the peforation, removes a layer of the material with its cutting lips. However, such an operation leaves burrs on the hole edges which deteriorate both the module itself and the connecting elements.
There is also known a device for disengaging the modules from the three-dimensional molecular model, which is essentially a thin metallic plate with a semiround recess at one of its ends. To disjoin the modules the recessed end of the plate is put in between the modules and the plate is pressed upon through a handle.
However, when pressure is exerted upon the tool and the latter works as a lever, an asymmetric moment of force arises, which affects adversely the model as a whole. Moreover, the device cannot be applied for assembling the model (cf., e.g., an advertising prospectus "Precision Molecular Models", The Bailing Corporation, South Natick, Mass., 1980, 67-7120, p. 3, 17).